Thread cutters for sewing machines



Feb. 12, 1957 1.. J. KUHAR THREAD CUTTERS FOR SEWING MACHINES Filed June23, 1954 IN VEN TOR.

Ludwig J Kuhar ATTORNEY United States Patent THREAD CUTTERS FOR SEWINGMACHINES Ludwig J. Kuhar, Clark Township, N. 1., assignor to The SingerManufacturing Company, Elizabeth, N. .L, a corporation of New JerseyApplication June 23, 1954, Serial No. 438,775

4 Claims. (01. 112-452 This invention relates to sewing machines andmore particularly to a thread cutter especially adapted for severing theneedle and bobbin threads after the termination of a sewing operation,and one of the primary objects of the invention is to provide animproved device of this class.

Another important object of the invention is to provide an improvedthread cutter that can be manufactured with the minimum of cost andeffort.

With these and other objects in view, as will hereinafter appear, theinvention consists in the devices, combinations and arrangements ofparts described in connection with the accompanying drawings, whichillustrate a preferred embodiment of the invention and in which:

Fig. 1 is a fragmentary perspective view of a sewing machine embodyingthe invention;

Fig. 2 is an enlarged view of a portion of the presserbar bushing shownin Fig. 1; and

Fig. 3 is a sectional view taken on the line 3-3 of Fig. 2.

Referring in detail to the drawings, the illustrated embodiment of theinvention is shown as applied to a familytype sewing machine of the typefully disclosed in United States Patent No. 2,617,375, issued November11, 1952. The present drawings illustrate portions of the sewingmachine, including a bed 16 to which there is hinged an extension plate17. The bed 16 is cut away and thereby receives a throat-plate 18 whichis held to the bed 16 by screws 1919. A presser-foot 21, of Well knownconstruction, is positioned above the throat-plate 18 and is pivotallysupported on the lower end of a resser-foot shank 22, the upper end ofwhich is held to the lower end of a resser-bar 23 by means of a thumbscrew 24. The presser-bar 23 is supported for longitudinal movement in aresser-bar bushing or tubular member 27, which, in a well-known manner,is supported in and extends below the lower end of a bracket-arm head28. The head 28 also supports a reciprocable needle-bar and needleindicated generally by the numeral 29.

The bushing 27, as best seen in Fig. 2, is in the form of a rightcylindrical tube and thus provides a tubular wall 31 having an innercylindrical surface 32 and an outer or external cylindrical surface 33.The base of the bushing is in a plane that is at right angles to theaxis of the bushing 27. The wall 31 surrounds a bore 34, which is thebore in which the presser-bar 23 is movably mounted. The upper end ofthe bushing 27 has a shoulder 36 and the lower end of the bushing 27 isprovided with an inclined thread-receiving slot 37 cut downward andinward toward, but not into, the bore 34 of the bushing. The slot 37base bottom 38, a lower arced edge 41, and an upper arced edge 42.Reference to Fig. 2 shows that the slot 37 is positioned in the wall 31of the bushing 27 in such a manner that the two ends of the slot 37 areat unequal distances from the bottom of the bushing 27, the upper end ofthe slot being indicated by the numeral 43, and the lower end of theslot being indicated by the numeral 44. By reference to Fig. 1, it willbe noted that 7 2,781,012 Patented Feb. 12, 1957 the lower end 44 of theslot 37 is located substantially in line with the line of feed of thesewing machine and that 'ice the upper end 43 of the slot issubstantially in line with p the end of the bracket-arm head 28. Inother words, the slot 37 subtends an are, measured circnmferentially ofthe bushing 27, of substantially ninety degrees Reference to Fig. 3shows that the sides of the slot 37 define parallel planes whichintersect, at an angle of approximately sixty degrees (60), a planedefined by the end or base of the bushing 27, the last named plane beingnormal to the longitudinal axis of the tubular bushing 27 Reference toFig. 2 shows that the bottom 38 of the slot 37 defines a line whichintersects the plane, defined by the end or base of the bushing 27, atan angle of approximately thirty degrees (30). This positioning of theslot 37 has been found to be especially advantageous when the slot isused to cut or sever the needle and bobbin threads at the termination ofthe sewing operation. Furthermore, the slot 37 opens only to theexternal surface 33 of the bushing 27 and is not cut deep enough tointersect the inner surface 32 thereof. This arrangement prevents lintor other dirt which may collect in the slot 37 from interfering with theoperation of the presser-bar 23.

The low cost of providing the thread cutter slot 37 in the bushing 27 isof considerable importance. first place, the bushing 27 is a standardpart of the sewing machine and would be supplied as a necessarycomponent of the machine whether the thread cutter was furnished or not.In the second place, the only operation that is required in providingthe thread cutter is the forming of the slot 37 by one saw out prior tofinishing the external surface 33 of the bushing 27. The grindingoperation, which is normally performed to provide the proper outsidediameter for the bushing 27, sharpens the thread-cutting edges 41, 43and 44 of the slot 37.

In operation, the thread cutter is used in the following manner. At thecompletion of a seam the upper and lower threads (not shown) are drawnout sufiiciently sothat they are long enough to reach the bushing 27above the slot 37. Then the threads are manually pulled against the sideof the bushing 27 at a level above the threadreceiving slot 37,following which a downward pull on the threads causes them automaticallyto enter the threadreceiving slot. Then a downward pull is exerted onthe threads and one or more of the cutting edges 41, 43 and/or 44 cutthe threads.

Having thus set forth the nature of the invention, what I claim hereinis:

1. A sewing machine comprising a bed, a bracket-arm head overhangingsaid bed, and a right cylindrical member supported from and extendingbelow the lower end of said bracket-arm head, said member being providedtoward its lower end with a thread-cutting slot cut into the member fromthe outer cylindrical surface thereof, said slot having a closed bottomthat defines a line which intersects a plane normal to the longitudinalaxis of the member at an angle of approximately thirty degrees (30).

2. A sewing machine comprising a bed, a bracket-arm head overhangingsaid bed, and a right cylindrical member supported from and having anouter surface extending below the lower end of said bracket-arm head,said member being provided toward its lower end with an upwardly open,downwardly extending thread-cutting slot cut into the member from theouter cylindrical surface thereof, the sides of said slot definingparallel planes which intersect a plane normal to the longitudinal axisof the member at an angle of approximately sixty degees (60).

3. A sewing machine comprising a bed, a bracket-arm head overhangingsaid bed, and a member supported from and extending below the lower endof said bracketarm head, said member being provided with a thread- Inthe cutting slot cut into the member from the outer surface thereof,said slot having a closed bottom that defines a line which intersects aplane normal to the axis of the member at an angle of approximatelythirty degrees (30) and the sides of said slot defining parallel planeswhich intersect a plane normal to the axis of the member at an angle ofapproximately sixty degrees (60).

4. A sewing machine comprising a bed, a bracket-arm head overhangingsaid bed, a member supported from and having an outer surface extendingbelow the lower end of said bracket-arm head, said member being providedwith References Cited in the file of this patent UNITED STATES PATENTS280,970 Staples July 10, 1883 1,251,352 De Voe Dec. 25, 1917 2,558,039Carrol] June 26, 1951

